In recent years, for example, HDMI (High Definition Multimedia Interface) has been gaining popularity as a communication interface through which digital video signals, that is, uncompressed (baseband) video signals (hereinafter, referred to as “image data”), and digital audio signals associated with the video signals (hereinafter, referred to as “audio data”) are transmitted at high speed from a DVD (Digital Versatile Disc) recorder, a set-top box, and other AV sources (Audio Visual sources) to a television receiver, a projector, and other displays. The details of the HDMI standards are described, for example, in Patent Document 1.    Patent Document 1: WO2002/078336